Associations of ambient air pollution with influenza virus activity in a subtropical city

Abstract

BACKGROUND: It is evident from experimental studies that air pollutants could facilitate the transmission of influenza viruses and also increase the severity of infections. However, few studies have addressed the effects of air pollutants on influenza virus activity in the community. OBJECTIVES: We assessed the temporal association of air pollutant concentration with influenza virus activity during 1998-2008 in Hong Kong METHODS: We fitted a Poisson regression model of influenza virus activity on the explanatory variables of ambient concentrations of four air pollutants: particulate matters with the aerodynamic diameter less than 10μm (PM10), sulfur dioxide (SO2), nitrogen dioxide (NO2) and ozone (O3). Virus activity was measured by weekly proportions of positive influenza isolates in specimens sent for making diagnosis to the microbiology laboratory of Queen Mary Hospital. The dose response relationship between air pollution and influenza was assessed by natural spline smoothing functions. RESULTS: The weekly concentrations of air pollutants showed one big peak in January/February and a small peak in May. This pattern was similar to the seasonal pattern of influenza virus activity. Influenza activity was significantly (p<0.05) associated with SO2 in a linear manner within the range of 0 -30μg/m3, as well as with O3 after reaching 20μg/m3. However, the associations of influenza virus activity with PM10 and NO2 were not statistically significant. CONCLUSIONS: Air pollutant concentrations were associated with influenza virus activity in the community of Hong Kong, suggesting that air pollution may be an environmental factor that regulates the seasonal outbreaks of influenza in the subtropical climate.